1. Field of the Invention
The invention relates to optical systems designed only for direct viewing by the eye of an observer. This includes passive devices like telescopes, microscopes and the like. It also includes active devices like infrared viewers, wherein a weak IR image is converted to a strong visible image by combinations of image intensifiers, photocathodes, photodiodes, cathode ray tubes, light emitting diodes (LEDs), etc. In particular it pertains to wide-angle viewers such as the peephole viewers found in residential front doors.
2. Description of Prior Art
Most IR imaging systems include displays featuring miniature image sources viewed through eyepieces. These eyepieces are designed with only a small amount of eye relief, so that, when it is desired to mount a monitoring device like a video camera using an image splitter, there is no longer room for the human eye. The Army""s Night Vision Laboratory recently obtained a commercially available device to mount such a camera, but it seriously degraded the field of view and has therefore not been satisfactory. The Laboratory at the same time has received requests from law enforcement agencies for a related optical device that can be placed over a peephole lens found in many residential doors. The device would obscure the view from inside, while providing a wide view of the interior from the outside. The present invention addresses both of these problems.
A peepscope for an imaging device, the peepscope""s lenses being housed in a common tube centered on a main optical axis coaxial with the optical axis of the imager. The lenses consisting of first and second eyepieces with their objective lenses facing each other, thereby providing identical input and output common tube ends. The tube may further include an optional framed side window centered on a secondary optical axis that intersects the main axis at a reflection point adjacent to and defining the tube""s input end. The viewer may also include an optional beam-splitter centered on the main optical axis at the reflection point forming an image through the side window, to accommodate a camera supported by the window""s frame. The peepscope may also include an optional central optical processor centered between the objective lenses, which can intensify and/or invert an input image formed by the eyepiece nearest the reflection point. Finally, the input and output ends of the common housing tube may be fitted with eyecups or similar adapters to bridge the gaps between the observer and the imager.